What Is IMAP (Internet Message Access Protocol)?

IMAP (Internet Message Access Protocol) is a protocol for synchronizing e-mail.  IMAP keeps a directory structure of all users. Therefore it is much more complex than POP3. A user agent, such as Microsoft Outlook Express and Thunderbird, for example, can therefore only a header clearance, or a portion of a message. This is useful, for example, if you mail via a slow connection or lock up on a PDA.

Another big advantage of IMAP is that the mail stays on the server so it is possible from any location with an IMAP program to log and view all mail. This is a big difference from the POP3 mail protocol that always has to pick up.

A recent extension of the so-called IMAP IMAP Idle command, which push e-mail is possible (in other words, a new e-mail is immediately visible on the client, and not only after the client’s decision to get).

IMAP was designed by Mark Crispin in 1986 as a replacement for POP.

IMAP

In the original version of IMAP IMAP is defined as “Interim Mail Access Protocol. This protocol is not used on the Internet.

IMAP2

The original IMAP protocol was soon replaced by imap2. Besides the change in technology was another acronym meaning, namely “Interactive Mail Access Protocol. Imap2 IMAP was the first version that was distributed.

IMAP4

As the name IMAP3 already used by another project, after imap2 IMAP4 delivered. The abbreviation was again changed to “Internet Message Access Protocol. After 2 years later revision 2 IMAP4 delivered.

IMAP4rev1

IMAPrev1 is compatible with imap2.

Unlike many other Internet protocols supported IMAP4 all encrypted login systems. It is also possible to encrypt IMAP using SSL. Normal IMAP traffic runs on port 143, SSL-encrypted IMAP traffic goes through port 993.

~Source: Wikipedia